Studies on the Factors Affecting Cellular Spreading Upon Culture-Substrate

Abstract

The effects of various divalent cations on cellular spreading of in vitro cultured fibroblasts of chick embryos upon substrates were investigated in serum-free Eagle's MEM. Fibroblasts spread on the surfaces of culture dishes in the presence of Mn2+, Mg2+, Ca2+; or Co2+, but not in the presence of Zn2+, Cd2+, Sr2+ or Cu2+. The minimum cation concentration for permitting cellular spreading at 37 °C is different for each cation. The values are 10-6, 5 x 10-4, 10-3 and 10-2M for Mn2+, Mg2+, Ca2+ and Co2+, respectively. Below these concentrations the cells remain round. Mn2+ is about 1000-fold more effective in causing spreading than Ca2+. The cells do not spread at low temperature, but they do at 22 °C in the presence of 10-4M Mn2+. In a medium conditioned with a mass culture of fibroblasts, cell spreading occurs at one tenth of the cation concentrations given above. If conditioned medium is heated at 65 °C for 30 min or treated with trypsin, its effect is abolished; this suggests that the effective factor(s) in the conditioned medium is a protein.